Document U.S. Pat. No. 5,652,838 describes an example of a method using such an electronic security device, specifically integrated in an optical disk. The input interface is constituted by light sensors adapted to detect the read laser beam of a computer using the optical disk, which laser beam is controlled so that the sequence with which it strikes the light sensors corresponds to an input code. The output interface of the optical disk is constituted by a screen which displays an output code as a function of the input code it receives from the computer. The user needs to take the optical disk out from the reader in order to read the output code, after which the user types this code on the keyboard of the computer, thereby authorizing use of the optical disk by the computer. This provides protection against illicit copies of the optical disk.
Those arrangements appear most attractive since they enable information to be sent to the optical disks using the read beam that is already available for reading the disk.
Unfortunately, those arrangements present the drawback of requiring light sensors to be placed in the data area of the disk in order to enable the sensors to receive the read beam, thus giving rise to constraints as to how data is positioned in said data storage area and putting limits on the capacity of said data area.
Furthermore, that solution is usable only with an optical disk and not with an electronic security device integrated in some other data medium or constituting a self-contained appliance independent of a data medium.